This invention relates to an engine control that breaks the torque lock typically found in a transmission with engaged gears, allowing the transmission to be moved to neutral without actuating the clutch.
Heavy vehicles, such as trucks typically have an engine driving the wheels of a vehicle through a multi-speed transmission. The transmission is moveable through several speed ratios at the control of a manual stick shift.
A manual transmission typically slides toothed members relative to different gears to engage one of the gears. To complete a shift, the operator must first typically move the gear that is presently-engaged out of engagement to a "neutral" position. In the "neutral" position, the transmission does not engage any gear, and thus rotational drive is not transmitted to the transmission output shaft from the engine shaft.
This movement from an engaged position to a neutral position occurs while drive is being transmitted. The toothed member moves to effect this change. When the transmission is engaged and rotational drive is being transmitted from the engine to the transmission, there is a large torque load holding the gears and the toothed member at a particular axial position. This torque load makes it quite difficult for an operator to manually move the toothed member out of engagement. This so-called "torque lock" typically makes it impossible to move a transmission to neutral without somehow reducing the torque load. To this end, vehicles with manual transmissions are equipped with clutches. An operator actuates the clutch which breaks the drive transmission from the engine to the transmission. The torque load goes to zero, and the operator is able to move the gear out of engagement.
In the heavy vehicle industry, the operation necessary to complete a shift between gears is relatively complicated. Typically, a driver must actuate the clutch, and then begin modifying the engine speed through the accelerator to synchronize engine speed to a speed necessary for the next speed ratio to be engaged. At the same time, the operator must manually move the gear shift lever to engage the gear in the proper new gear. These procedures become more burdensome when a driver is rapidly shifting through several sequential gear changes.
Recently, heavy vehicles have become equipped with more and more controls that require operator-intensive operations. At the same time, the experience level of operators is decreasing. Thus, it would be desirable to reduce the steps an operator must make on a routine basis when driving. To this end, it would be desirable to allow the operator to move the gear out of engagement for a shift without having to actuate the clutch.
One prior system proposed achieving a zero torque load by measuring the actual torque, and controlling the engine to attempt to reach a zero torque load. This proposed system would be too complex to be practical. The placement of the torque meter would be costly and lead to frequent repairs. Moreover, an exact measurement of the zero torque value would be difficult to utilize, as it changes with time. Finally, this proposed system does not allow an operator the option of not using the torque-breaking feature and relying upon clutch operation.